Photographic print-out process utilizing binder-free silver fluoride



April 7, 1970 J, M. P s 3,505,066

. PHOTOGRAPHIC PRINT-OUT PROCESS UTILIZING BINDER-FREE SILVER FLUORIDEFiled Oct. 5. 1966 2% x -SUPPORT L X L 267" ,7 ,7/ yyyyyyyyyyyy 22 J I,1/ I, ll I I 1' 1 1 1 1 r 1 HG IIIIIIIIIIII VACUUM DEPOSITION OF GOLDIIIIIIIIIIII VACUUM DEPOSITION OF SILVER 26 PHOTOSENSITIVE STRATUM I I II I I I I I I I I l IIl r glLeER BF3 VAPOR FLUORIDE FIG 2 osve LOPEDNEGATIVE EXPQSED AREAS FROM EXPQSURE TO LIGHT CONTAINING ULTRAVIOLETRADIATION INVENTOR.

Guam and M and ArrorInsvs United States Patent 3,505,066 PHOTOGRAPHICPRINT-OUT PROCESS UTILIZ- ING BINDER-FREE SILVER FLUORIDE Joel M.Peisach, Hudson, Mass., assignor to Polaroid Corporation, Cambridge,Mass., a corporation of Delaware Filed Oct. 5, 1966, Ser. No. 584,447Int. Cl. G03c 1/02 US. C]. 9627 5 Claims ABSTRACT OF THE DISCLOSUREPrint-out images may be obtained by exposure of silver fluoride stratato ultraviolet radiation. The silver fluoride stratum is preferablyprepared by BF treatment of vacuum deposited silver. The print-out imagedensity may be increased by heating after exposure.

The present invention relates to novel photographic processes, and moreparticularly to the formation of photographic images by print-outprocesses. The primary object of the present invention is to provide aprint-out process employing a photosensitive element comprisingphotographic materials formed at least in part by the vapor fluorinationof silver coated substrates.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the process involving the severalsteps and the relation and order of one or more of such steps withrespect to each of the others which are exemplified in the followingdetailed disclosure, and the scope of the application of which will beindicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection withthe accompanying drawings wherein:

FIGURE 1 shows successive diagrammatic cross-sectional views of thepreparation of typical photosensitive elements utilizable in the presentinvention, said elements being prepared for example by the processdescribed and claimed in the copending application of Paul D. Lubin andJoel M. Peisach, Ser. No. 584,412, filed concurrently herewith.

FIG. 2 shows an exaggerated cross-sectional view of an element preparedby a process such as that described in FIGURE 1 being used in accordancewith the present invention.

The silver halide substrates that are utilized in the process of thepresent invention are unique and different from the prior art in thatthey contain some form of a silver fluoride as part of thephotosensitive material. Heretofore, the photographic art had generallyconsidered silver fluorides to be light insensitive and, therefore, ofno importance in photography. Reference is made to Light- SensitiveSystems, by Jaromir Kosar, published 1965 by John Wiley & Sons, Inc.,New York, NY. Particular reference is made to pages 18 and 19. Silverfluoride is known to exist in three forms, namely AgF, Ag F and AgF Allof these are water soluble. See the 41st edition of the Handbook ofChemistry and Physics published by the Chemical Rubber Company, at page648. The existence of other forms or complexes of silver and fluorineare not known and can only be theorized. It is because of this watersolubility factor that silver fluoride was not utilized in the prior artto prepare a silver halide emulsion by the techniques usually employedwith the other silver halides. It is seen, therefore, that the abilityto prepare such photosensitive silver fluoride strata and theutilization of these photosensitive strata to obtain a photographicimage would, indeed, be unique and unexpected.

In view of the fact that the known forms of silver fluoride are watersoluble, it seems apparent that the silver fluoride photosensitiveelements to be utilized in the present invention must be prepared in amanner wherein water is excluded.

The silver fluoride photosensitive elements utilized in the presentinvention are best prepared by the deposition of metallic silver upon asupport followed by contracting the silver coated support with borontrifiuoride vapors. Particularly beneficial strata for utilization inthe present process are those wherein the silver is vacuum deposited,i.e., by evaporation or sputtering techniques.

A photosensitive element that gives rise to excellent results in thepresent invention is one wherein gold is vacuum deposited in conjunctionwith the vapor deposition of the silver prior to the boron trifluoridevapor treatment.

A suitable vacuum deposition process is described in United StatesPatent No. 3,142,566 to Edwin H. Land, granted July 28, 1964.Apparatuses necessary to prepare such products are well-known in theart. A typical example of such a machine is described in the book VacuumDeposition of Thin Films, by L. Holland, published by John Wiley & Sons,Inc., New York, N.Y., 1948, pp. 7 and 8.

Photosensitive elements utilizable in the present invention may beprepared on a variety of substrates. These support materials include anysuitable paper such as baryta paper or any suitable plastic such aspolyethylene terephthalate sold under the trade name Mylar or Cronar byE. I. du Pont de Nemours & Company, Wilmington, Del. Cronar is believedto be polyethylene terephthalate subcoated with what is described as awater permeable colloidal layer such as is set forth in United StatesPatent Nos. 2,627,088 and 2,698,242. As is known in the art, subbinglayers may be provided for a multitude of purposes. Methods forpreparing such subbing layers on base materials are well known and neednot be described herein.

Photosensitive strata containing silver fluoride can be developed to anegative silver image by exposure of the photosensitive stratum to alight source containing ultraviolet radiation. Typical light sourcesthat contain such UV radiation are a xenon lamp and conventionalphotoflood lights which are generally available in commerce. The processof the present invention utilizes print-out exposure techniques. In thisprocess the image forming subject is placed in contact with thephotosensitive stratum and a photo exposure is made. Subsequent to theexposure, an image will appear. It is thus seen that wet development ofthe photo exposed stratum is unnecessary. Ofttimes, heat can be utilizedin conjunction with the light to intensify the image.

The process of the present invention gives rise to a high resolutionmaterial with low speed and as such can be utilized in stellarphotography.

The following examples are set forth to illustrate this invention andare not intended to be limiting.

The subject matter set forth in Examples I and II is claimed in Ser. No.584,412.

EXAMPLE I FIGURE 1 illustrates the production of a photosensitiveelement utilizable in the present invention. Gold was vacuum depositedby being evaporated uniformly onto a sheet of nnsubbed Mylarapproximately 0.014 inch thick, 4% inches wide and 15 inches long toform a gold stratum 22 with a coverage of approximately 10 mg. persquare foot. Then silver was vacuum deposited by being evaporated ontothe support coated with gold to form a gold and silver stratum 24, witha coverage of about 60 mg. per square foot of silver.

This sheet was then placed in a desiccator which was then evacuated atroom temperature. The vacuum was broken by the introduction of 9 litersof boron trifluoride gas (equal to 27 grams of B1 at room temperatureand atmospheric pressure). The sheet was left in the boron trifluorideatmosphere for 20 hours. The so treated sheet was translucent indicatingthe formation of a silver fluoride photosensitive stratum 26.

EXAMPLE 11 Silver was vacuum deposited by evaporation onto a sheet ofCronar film to provide a stratum having a silver coverage ofapproximately 20 mg. per square foot. This sheet was placed in adesiccator which was then evacuated at room temperature. The vacuum wasbroken by the introduction of boron trifiuoride gas into the system. Thesheet was left in this BF atmosphere for six hours. The sheet becametranslucent indicating the formation of a silver fluoride.

EXAMPLE III A photosensitive element comprising silver fluoride onbaryta paper was exposed to a light source containing UV radiation forapproximately 2 minutes. Upon removal of the light source the imageformed from a high contrast object became visible.

EXAMPLE IV A photosensitive element comprising silver fluoride on asubstrate of Mylar was exposed to a Number 2 Westinghouse Photoflood forapproximately one minute. This element was then subjected to heat withinthe range of 80 F. to 180 F. for about minutes to intensity thepreviously formed image obtained from a conventional step-wedge.

EXAMPLE V A photosensitive element containing silver fluoride wasexposed to long-wave ultraviolet radiation from a Model X4 Blak Ray madeby the Ultraviolet Products Company, Incorporated, San Gabriel, Calif.,for one minute at a distance of 2 inches. An image of moderate accutancebecame visible immediately upon removal of the light source.

Photosensitive materials utilized in accordance with this invention arecharacterized by negligible grain, relatively low sensitivity, e.g., anexposure index of less than ASA 1 and by the formation of imagesexhibiting long soft or low contrast, curves.

It will be readily appreciated, that the binder-free silver fluoridephotosensitive element should be prepared by a process whereinsubstantially no water is present, in view of the previously discussedfact of silver fluoride solubility in the Water. Typical reagents thatcan be utilized to fluorinate silver include H-F, F and B1 Theadvantages to be derived from the use of the boron trifiuoride,

in the vapor state as opposed to the HF and F gases include easyavailability in commerce, relative ease of handling, the relativefreedom from toxicity, and the ability to use conventional reactionvessels.

The term binder-free is utilized to signify the fact that thephotosensitive elements used in the present invention are preparedwithout gelatin or an equivalent binder as is used in conventionalphotographic materials. In certain instances, however, it may bedesirable to apply a stratum of a polymeric material over the surface ofthe binderfree photosensitive element, in which event the silverfluoride will still be substantially binder-free.

Since certain changes may be made in the above process without departingfrom the scope of the. invention herein involved it is intended that allmatter contained in the above description and accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. The process of forming a visible image comprising exposing abinder-free stratum of silver fluoride to ultraviolet radiation until aprint-out image is formed, said silver fluoride stratum having beenprepared by fluoridation of vacuum deposited silver.

2-. The process of claim 1 wherein said vacuum deposited silver wasdeposited on a stratum of vacuum deposited gold.

3. The process of claim 1 wherein said photosensitive stratum issubjected to heat subsequent to said photo exposure.

4. The process of forming a visible image which comprises exposing aphotosensitive element to a light source containing ultraviolet light,said photosensitive element having been prepared by the reaction ofboron trifiuoride with silver, said silver having been vacuum coated ona support, and heating the photo exposed element within the range of F.to F., subsequent to said exposure, to intensify the image.

5. The process of claim 4 wherein the silver coated substrate furtherctontains metallic gold.

References Cited UNITED STATES PATENTS 1,5 60,240 11/ 1925 Jelley 96-943,142,566 7/1964 Land 9694 3,142,567 7/1964 Morse 96-94 FOREIGN PATENTS547,806 9/1942 Great Britain.

J. TRAVIS BROWN, Primary Examiner US. Cl. X.R.

